The problem I have with relying on simple pack voltage measurement to control the charger is that eventually, as the pack ages, one or more cells are going to go out of balance, become the 'weakest link' and cause the capacity of the pack as a whole to unnecessarily reduce. From a safety perspective (safety of the pack) I suppose the Light-meter method is as good as any but it is the vagueness of its operation that is the issue for me.
Maybe we'll see that cells of certain types simply don't change their behaviour relative to the rest in a given pack but it seems unlikely. If the pack does go out of whack then it is going to be a potential pain to balance them manually. But for some the cost saving of not having a BMMS may outweigh the agro. MW On 12 Oct 2014, at 22:11, Paul Dove via EV <[email protected]> wrote: > Problem is no one has actually proved that with experimentation. Not in any > of my reading. You can believe what ever you like. > > I have used ammeter for 2 years now. The voltage always end exactly the same. > The next day the pack is the pack is exactly 147 volts. > > I have never seen any study done on top balancing lithium batteries. I would > love it if someone should come up with one. That a left over procedure from > lead acid batteries on which it actually works. > > Sent from my iPad > >> On Oct 12, 2014, at 4:02 PM, Cruisin via EV <[email protected]> wrote: >> >> Using a meter to turn off a charger at a pre-programmed voltage can be very >> risky. A BMS is designed to perform this function, but turns off the charger >> when a single cell reaches the pre-programmed voltage, after permitting all >> cells to achieve the same voltage by shunting. It also protects against over >> dis-discharge. A single meter cannot perform these tasks in anyway shape or >> form. The SOC meter provides all the information concerning usage and is >> VERY accurate and programmable. All American electric production cars use >> very sophisticated BMS systems to achieve longevity due to a mandatory >> 8-year 100k mile warranty required in CA. Don't risk a expensive Li-ion >> battery pack by relying on a meter to shutoff the charger at a set voltage. >> Could be used as a backup if desired. If we learn from the big guns on how >> they do it, we will be on the right track and prevent a disaster that too >> many can attest to. My 2-cents worth. >> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
